The purpose of this study is to determine the effect of various weights on the pharmacokinetics of vancomycin (a community used antibiotic for gm(+) infections). Body composition will be measured by bioelectrical impedance and anthropometric means in 40 patients of various weights. After receiving a single lg dose of vancomycin and serial blood samples will be collected, and the volume of distribution and clearance vancomycin will be determined. An equation for dosing obese patients based on body composition will be determined.